My view as an animal rights litigator who was one of the attorneys behind a federal judge declaring Colombian hippopotamuses to be legal “persons” for the limited purpose of being able to apply for a subpoena in the United States:

The word “person” has many different understandings depending on the context, and this is the source of much confusion.

The common usage of the word “person” equates being a person with being a human. And people starting with that common understanding will naturally tend to think that being a “legal person” means having the same (or similar) legal rights as a human.

The problem with that definition of a legal person though is that even between humans legal rights and duties vary dramatically. Compare the legal rights that a U.S. court would give a non-citizen infant who is located in another country (the right to travel here maybe, the right to apply for asylum maybe) with the legal rights that U.S. court would recognize for an adult who is a citizen. And even between adults who are citizens, some may not be able to drive if they can’t pass a driver’s test, and some may even be sujbect to getting killed by the government if they were found guilty of murder in some jurisdictions in the U.S. Consider further the differences between legal rights of humans in the U.S. based on age, incarceration status, what state they live in, and whether they are currently elected to public office in the government with the right to vote on or sign legislation into law for example.

Additionally, this view of legal personhood as being roughly the same as having the same legal rights as a human does not make sense as-applied to corporations. Corporations can be bought, sold, and owned. Corporations can be terminated by a vote of the board, or by a state’s Secretary of State for failing to comply with proper paperwork like renewing registration every year. At the same time, it is useful for corporations to have some legal rights and duties. A corporation can enter into a contract to take out a loan or construct a new office building, and it makes more sense for the corporation to do that than for one of its employees to have to personally apply for a loan or personally sign a contract to build a new office building. It is also useful to be able to sue corporations when they do things like rip us off or hurt us illegally. Where we get into trouble is actually when we conflate corporate personhood with human personhood and give them the right to donate money for political speech and the right to freedom of religion that arguably should only go to individual humans and not to corporate entities.

So what is legal personhood and when should it be recognized? I contend that legal personhood just means that a court recognizes that you have some legal right(s) and/or obligation(s) that can be enforced in court. Essentially, that you have a legal “personality” and the ability to be a litigant in a lawsuit. So really the key questions are whether the law recognizes that a given entity has some legal interest that must (or should) be recognized by courts.

By that definition, I’d argue that animals already are legal persons, albeit in a very weak sense. Animal cruelty laws exist in all fifty states to protect animals from unjustified neglect and abuse. That is clearly a legal interest and legal right that animals possess in my view. Therefore, courts should recognize that animals have legal interests and legal standing to be litigants in legal proceedings relating to enforcement of laws intended to protect animals. We should be asking courts to do that, courts should be recognizing that animals have legal rights and legal personality, and to the extent courts fail to do this legislatures should step in and correct courts.

ETA: Under that framework, the question of legal personhood at least is really an empirical question about whether the entity in question has legal interests that can be the subject of legal proceedings. There is a slight normative dimension to the question as well though to the extent that the issue has not been unequivocally decided in a jurisdiction a judge will have to ask “should or does the law recognize that this entity is a legal person for purposes of this dispute?” That kind of brings us into the territory of asking what is the nature of law: is it judges somewhat just making stuff up as they go (legal realism / more normative) or is it judges dutifully applying the law to the situation at hand (legal positivism / more empirical). But that’s a whole other discussion.